As disclosed in JP-A-2000-34960, a fuel supply apparatus of in-tank type is well known, which places a fuel pump within a fuel tank. In this type of fuel supply apparatus, residual fuel level in a fuel tank is detected by detecting interface of the fuel stored in the fuel tank or a sub-tank contained in the fuel tank. To do this, a fuel supply apparatus has a float member, which floats on the fuel, and a detector for detecting the level of the float member. A detector may be mounted on a lid member for attaching the fuel pump to the fuel tank, a bracket for supporting the fuel pump from the opposite side of the lid member, or a filter case of the fuel pump.
However, since the detector is predetermined to be on a lid member, bracket or fuel pump, mounting position of the detector may not be easily changed. For this reason, depending on the shape of the fuel tank or sub-tank to which a fuel supply apparatus is applied, a float member may interfere with the fuel tank, sub-tank or suction filter for removing foreign substances contained in the fuel. In order to avoid the interference of the float member with the fuel tank, sub-tank or suction filter, a lid member, bracket or fuel pump of different design should be provided for each of shapes of fuel tank to which the fuel supply apparatus is applied. Therefore, it is difficult to standardize the components and design of a fuel supply apparatus.